Testing systems for integrated circuit devices not only provide quality control information but also provide valuable feedback to electronic systems designers. Testing systems are used to test the DC and AC characteristics of a particular integrated circuit device. In addition, more complex tests are used to test the internal timing of the device. For example, tests such as the set-up and hold tests determine how long signals must remain in a steady state in order for other processes within the integrated circuit to function responsive to those signals. In addition, tests such as the minimum pulse width and maximum frequency tests determine how short a clock signal pulse and high a frequency of a clock signal a particular integrated circuit device may use and still function properly.
In the past, testers have performed functional tests which set a particular parameter and determined if a particular integrated circuit device passes or fails based on these parameters. These functional tests are useful in quality control in the sense that they can determine whether a particular integrated circuit will operate under particular operating conditions. However, functional tests are not as useful to provide feedback to designers because they do not determine the extent to which a particular circuit has passed or has failed.